Story highlights

NASA says Scott Kelly is 2 inches taller after spending nearly a year in space

He's about to reunite with his twin brother in Houston

Since his return to Earth, the astronaut has been sharing photos of life on the ground

CNN  — 

Astronaut Scott Kelly and his twin brother used to be the same height.

But it’s likely that won’t be true when the two stand side by side for the first time in nearly a year.

NASA’s Jeff Williams told CNN that Scott Kelly grew 2 inches during his time aboard the International Space Station

It was expected, and it’s temporary, Williams said.

“Astronauts get taller in space as the spine elongates,” Williams said, “but they return to preflight height after a short time back on Earth.”

Before that happens, Kelly may still have some time to gloat; he and his brother are set to reunite late Wednesday in Houston.

Though he’s no longer an astronaut, Mark Kelly volunteered to take part in NASA’s “Twins Study” with his brother. NASA wants to see how the identical twins measure up after a year in two very different environments: Scott in space and Mark on Earth.

Scott Kelly returned to Earth Tuesday after 340 days. It’s the longest any U.S. astronaut has been in space.

Since then, he has been getting reacquainted with his planet, posting a series of tweets about life on the ground.

He shared a photo of a sunset he glimpsed in Norway.

Then he posted a picture of a phone conversation with President Obama, who called to congratulate him on his record-breaking mission.

And after nearly a year sharing pictures of breathtaking views and high-tech equipment, Kelly did something Wednesday that showed he’s just like anyone else with a smartphone and a social media account.

He posted a photo of his lunch.

CNN’s Dave Alsup, Amanda Barnett, Jareen Imam, Joshua Berlinger and Ashley Strickland contributed to this report.